With advances made in the trend toward higher storage density of a magnetic head device, a track size for recording bits has kept on advancing toward miniaturization, and as a result, there has been an increasing demand for higher sensitivity with respect to a magnetic read head. As described in “Nikkei Electronics”, Vol. No. 774, (Jul. 17, 2000), pp, 177-184 (Non-patent Document 1), attention has lately been focused particularly on a magnetic read head, using a tunnel magneto-resistance (TMR) effect film, as a supersensitive magnetic sensor of the next generation. In Non-patent Document 1, there is disclosed a head structure wherein after fabricating a multilayered film formed by sequentially depositing an electrode, a soft magnetic free layer, a non-magnetic insulating layer, a ferromagnetic pinned layer, an antiferromagnetic layer for pinning the magnetization direction of the ferromagnetic pinned layer, and an electrode on a lower magnetic shield, the multilayered film is patterned so as to provide both sides thereof with a hard magnetic layer for stabilizing the magnetization direction of a non-magnetic free layer, and an insulating film for insulating an upper magnetic shield from the lower magnetic shield.
Further, as disclosed in, for example, Nature, Vol. 416, pp. 713 to 715, 2002 (Non-patent Document 2), there has lately been proposed a new type of TMR sensor, as a sensor making use of the TMR effect, wherein two multilayered films each comprised of an insulating layer and a ferromagnetic layer are formed at different locations on an Al metal electrode layer, and a current is caused to flow from the ferromagnetic layer of a first multilayered film to the Al metal electrode layer while polarized spin is diffused up to a portion of the Al metal electrode layer, directly underneath the other multilayered film comprised of the insulating layer and the ferromagnetic layer, thereby detecting a change in resistance, according to a change in the magnetization direction of the ferromagnetic layer of a second multilayered film.    [Non-patent Document 1] “Nikkei Electronics”, Vol. No. 774, pp. 177-184    [Non-patent Document 2] Nature, Vol. 416, pp. 713 to 715, 2002